(upbeat music) - Hello and welcome to
the third and final video in our Outlive series. Looking at the DEXA scan metrics of most interest to the book's
author, Dr. Peter Attia. Our first two videos
looked at the DEXA metrics of visceral fat and bone density. But it is Attia's third DEXA measurement that causes him the most concern. And that is muscle mass. The word muscle appears
over 200 times in the book, four or five times more than
the other two metrics combined. And two of them are in
this emphatic statement. "Continued muscle loss and inactivity literally puts our
lives at risk," he says. "Seniors with the least muscle mass are at the greatest risk
of dying from all causes." In an interview, he says
that muscle mass is a highly, highly predictive metric of
how long you're going to live. As with bone density, Attia
quotes a staggering statistic. This time, from a Chilean
study of 1,400 people with an average age of 74. Of those in the lowest
quartile for muscle mass, after 12 years, about
half of them were dead. Compared to just 20% in
the highest quartile. Let's now look at muscle mass
as measured by a DEXA scan. DEXA breaks body composition
into three compartments. Fat, bone and what is called lean mass. Because your lean mass is everything that is not fat or bone, it includes not just your muscles, but also your organs,
ligaments, connective tissue, skin and so on. It is standard practice, as Attia does, to read lean mass as if it were muscle. For one thing, about half or more of your
lean mass actually is muscle, and for another, the lean
mass that isn't muscle, like skin and organs, et cetera,
we don't expect to change. Now, a technical point. Attia often interchanges
lean mass and fat-free mass. They are similar, but not quite the same. Lean mass is just your
non-fat soft tissue, mainly muscle and organs. Whereas fat-free mass includes your bones. As you can see from this body scan report, because your bone weight is small, typically between a one-and-a-half and three-and-a-half kilos, lean mass and fat-free
mass are quite close. That said, fat-free mass is typically
about five percent more than your lean mass. At Bodyscan, we use lean mass, which is closer to muscle mass. Your DEXA scan then calculates
two indices for muscle and it is these data points
that Attia hones in on. They are known as your Lean Mass Index and your Appendicular Lean Mass Index, and appear on page one of your report. Your Lean Mass Index is
your total lean body mass, essentially muscle and organs, divided by your height squared. You could say it's your BMI for muscle. Because it is normalized for height, your LMI is a very good index for putting your total
muscle mass into perspective and comparing it to
the broader population. Attia's second data point, your Appendicular Lean Mass Index, is the same as LMI, but
for your limbs only. That is, it excludes your torso. He uses LMI and ALMI to
triangulate overall muscle mass. But he puts more emphasis on ALMI and regards it as a purer
measure of muscle mass because it's not skewed by
the lean mass of your organs. In one interview, Attia despairs about our
ignorance of the metric. "Most people don't know
their ALMI," he says. "They don't actually know
how much muscle they have. They don't know where they stack up for other people their age and sex." As for ALMI being a purer
measure of muscle mass than LMI, Attia has a point. But ALMI is the lean
mass of all your limbs, so it, too, has its own limitation, in that it doesn't
separate arms from legs. At Bodyscan, we go a step beyond ALMI, because we reveal your muscle distribution across arms, legs, and trunk separately. For example, this woman's ALMI is in a
higher percentile than her LMI, which we assume Attia
would take as a good thing. But when we plot her
full muscle distribution on our data tables, we find that her higher ALMI
comes from her legs only. Now, as Attia puts a lot of
emphasis on grip strength, you can see that ALMI on its own may not be granular enough
to make a proper assessment of muscle mass. Incidentally, an even muscle distribution is shown by the three lean data points for arms, trunk and legs, forming a line that is
close to the vertical. Here we see a man's uneven distribution, where the upper body, the trunk, carries significantly less muscle, relative to the arms and legs. So a higher ALMI than LMI. Now incidentally, when it comes to muscle, it is valid to use the percentiles based on US data within the report. That's because we all
have a natural set point when it comes to how much muscle we carry. Those people we might call
small, slight, skinny or petite, are in the lower
percentiles for lean mass. While those in the higher percentiles are what we might call big,
solid, chunky, or muscular. It is that naturalness of lean mass that makes US and UK data comparable when we allow for age, sex, and ethnicity. As an example, this Bodyscan client in
her 40s has an LMI of 16.2 and a US percentile of 60. Against Bodyscan's UK-based dataset, she's also in the 60th percentile. But we would never use US
percentiles for fat indices because body fat is influenced
by lifestyle and diet. Now, back to the book. And Attia says, "It is important to maintain
muscle mass at all costs. Because if we lose it in later years, it can be impossible to get back." That's probably why, in an interview, he says he wants his
patients' lean indices to be "north of the 75th percentile." That is, more muscle for their height, than at least 75% of
people of the same age, sex and ethnicity. The morbidity statistics suggests that's a goal worth aiming for. But in my view, it sits somewhere between
ambitious and impossible. As I mentioned earlier, our natural set point will determine which percentile we start in, and our genetic capacity will limit how much muscle we can gain. Building muscle is achieved
by resistance training, usually with heavy weights in a gym. But it is a slow process, and gets slower as we
reach our genetic limit. The simple fact is, not everyone can reach
the 75th percentile. This 31-year-old man may not
be at his maximum muscle, but it took him 27 months to gain just under five kilograms of muscle, taking him from the 53rd
to the 73rd percentile, just outside Attia's preferred target. From the thousands of
male and female scans we've done at Bodyscan, I would refer to the 80th percentile, not much above Attia's desired 75th, as equivalent to an amateur bodybuilder. Having said that, this 26-year-old natural male bodybuilder, who started lifting weights 10 years ago, has a Lean Mass Index still
only in the 72nd percentile, also short of where Attia wants him to be. Incidentally, note how his LMI and ALMI are
very close in percentiles, suggesting an even and
aesthetically balanced physique. The hard fact is, to get from the 10th
to the 75th percentile might take 10 kilograms or
more of muscle gain for a man, and eight kilograms or more for a woman. That's a lot. The other point worth
making about muscle mass is that when you remove the
resistance training program that got you there, you'll
lose all your gains, which is why Attia wants
us all to weight train for the rest of our lives. Attia also makes some
contradictory statements about muscle mass. In one, he says it peaks
as early as our late 20s, before beginning a slow steady decline. In another, he says muscle mass remains
relatively consistent from our 20s and 30s into middle age. The vast majority of Bodyscan's
customers are under 65. And until that age, our data suggests lean
mass remains fairly static. But after 65, Attia says, activity levels and muscle
mass decline steeply. And even more steeply after 75, which he describes as
"falling off a cliff." At age 80, he says, the average person will
have lost eight kilograms from their peak. Remember, though, that a DEXA scan measures
muscle mass, not strength. And Attia does differentiate the two. He says it's not enough to
build a big chest or arms. Your muscles need to be strong,
capable of generating force. He concludes it comes down to how much heavy stuff you can carry, and refers to carrying
as our human superpower. As well as carrying
kettlebells and dumbbells, Attia says he is
semi-obsessed with rucking. And I'll leave you to read the book to find out what that is. That concludes this video on muscle mass. The third and final video in our series, looking at Peter Attia's three
most important DEXA metrics for an improved lifespan and healthspan. Please check out the other two on visceral fat and bone density. We hope you've found this series useful and we look forward to
seeing you at BodyScan soon. Goodbye for now. (bright music)
